It is known in the production of microcontacts on a monolithically integrated microcircuit (chip) to connect the contact locations on the chip with one end of thin metal wires and to join electrodes to be connected to the chip with the other end of the thin metal wires by means of thermocompression or rubbing, thus producing deformable multiconnections (see, for example, Kastner, Halbleiter-Technologie [Semiconductor Technology], published by Vogel-Verlag, Wurzburg, 1980, pages 88,89). The joining electrodes may be spaced much farther apart on the chip substrate than the contact locations on the chip. The joining electrodes can thus be produced as plug-in contacts Although this results in a plug-in component which can easily be installed in or removed from a larger electronic switching unit, the installation surface required for this purpose still is a multiple of the chip surface.
It is also known to distribute the contact locations over the entire chip surface and to solder the contact locations of a plurality of chips directly onto a common ceramic substrate which contains the connecting conductors in several layers, this being known as "flip-chip bonding", as described, for example, by L. S. Goldman and P. A. Totta in an article entitled "Area Array Solder Interconnections for VLSI" in Solid State Technology, Volume 26, No. 6, 1983, pages 91-97. Using this technique, it is possible to realize significantly greater integration densities and significantly shorter signal delay times than with other installation methods. Because, the rear sides of the chips are free of mechanical or electrical structures in this installation method, there arises the additional possibility of cooling the rear sides with water in pressed-on metal cylinders.
The direct soldering of the chips onto the ceramic substrate, however, results in even greater mechanical stresses on the solder connections, particularly as the size of the chip increases, due to the different coefficients of thermal expansion of chip and substrate material upon changes in temperature. With a desired further enlargement of the chip surface and the further refinement of the conductor and connection structures, the danger of breaks in the rigid solder connections is considerably increased.
Further, in modern large size electronic devices it is necessary that components be mechanically separable into function groups so as to simplify maintenance, assure exchangeability of the groups and facilitate expansion. See, for example, A. Keil, W. A. Merl, and E. Vinaricky, Elektrische Kontakte und ihre Werkstoffe [Electrical Contacts and Their Materials], published by Springer Verlag, 1984, pages 317 et seq. Mechanical separability is realized by plug-in or press-on connectors having multiple connecting elements.
If mechanical separability is to exist for the installation of individual integrated circuits, or chips, considerable concessions must be made, at the present state of the art, with respect to integration density since conventional chip carriers provided with mechanically separable connecting elements, and their associated contact bases, require an area which is a multiple of the available chip surface. The connecting elements of the chip carrier are here connected to contact locations on the chip by way of relatively long conductors, e.g. according to the wire bonding method as described by Kastner, above. Here the joining electrodes on the chip carrier may be spaced considerably farther apart than the contact locations on the chip. Only in this way is it possible to mechanically plug in and separate the multiple connecting elements for electrically joining the microelectronic components.
If particularly high integration densities are desired, which is the case, for example, in the construction of particularly fast and high powered computer systems, mechanical separability of the chip connections must be relinquished at the present state of the art.
In the "flip-chip bonding" technique described by L. S. Goldman et al, above, the exchangeability of individual chips, which is obligatory for maintenance purposes or for a later change of functions, is realized by making available a special soldering device which operates with a hot gas jet (see, for example, K. I. Puttlitz, "Chip Replacement by Hot-Gas Site Dressing", published in Solid State Technology, November, 1980, pages 48-50). To assure avoidance of undue temperature stresses in the substrate and to effect the necessary smoothing of old solder locations requires a significant amount of apparatus and time.